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Annuals are a nice addition to a landscape because of the seasonal color they bring. They can be tucked into planters to fill in spaces among perennials, used in containers or stand alone in the landscape. Annuals that are commonly used are typically chosen for their ease of growth, minimal requirements and colorful flowering show. The annuals that are common to landscapes vary with season based on the type of conditions the plants best tolerate.

Cool-Season Blooms

Iceland poppy (Papaver nudicaule) and Nemesia (Nemesia spp.) can grow up to 12 inches tall with a variety of flower colors. Snapdragons (Antirrhinum majus) can grow from 6 to 24 inches tall depending on the variety with many flower colors. The taller-growing varieties make nice cut flowers. Pansies (Viola spp.), sometimes referred to as Johnny-jump-ups, come in many different colors and produce wonderful winter blooms. They make a nice border accent along with primrose (Primula spp.), which also come in a variety of colors.

Spring Blooms

Sweet William (Dianthus barbatus) is an annual but has some perennial varieties. The annuals can grow from 6 to 12 inches tall with white, pink or maroon flowers. Lobelia (Lobelia erinus) is traditionally lower growing with some varieties only 4 inches tall but can reach heights of 12 inches. The blue, purple and white flowers will dry out in extreme heat. Sweet peas (Lathyrus odoratus) are an easy annual to grow from seed. There are many color varieties that grow into a beautifully fragrant climbing vine, though bush varieties are also available. Sweet alyssum (Lobularia maritima) is easily reseeded and produces white, purple and pink blooms.

Warm Season Blooms

Cosmos (Cosmos bipinnatus) grows 12 to 24 inches tall and is great for attracting pollinators with its pink, purple and white flowers. This sun-lover reseeds easily. Marigolds (Tagetes species) are moderately drought tolerant and add a nice pop of color with orange and yellow blooms. Depending on the variety, they can grow 6 to 12 inches in height. Petunia (Petunia x hybrida) comes in a variety of colors and growth habits. They are drought tolerant which makes them an appealing addition to your summer flower garden. The poppy (Eschscholzia californica) is the state flower of California and is easily identified with its bright-orange blooms. It grows from 8 to 24 inches tall and reseeds easily, bringing the brilliant color back year after year. Portulaca (Portulaca grandiflora) is a low-growing annual, only reaching 8 inches maximum. It can produce a variety of colorful, roselike blooms on each individual plant. Zinnias (Zinnia spp.) are a common annual likely because of the beautiful variety of flowers, growth habits, heat tolerance and ability to attract pollinators.

Extending the Bloom Season

While there are general guidelines of when your annuals will bloom, this will vary depending on the environmental conditions and care given to your plants. These common annuals typically prefer full sun to afternoon shade. To extend the bloom season of your annuals, ensure the water requirements are met. Too much or too little water can cause stress to your plants and negatively affect growth and flowering. Remove spent blooms from your annuals, allowing the plants to direct energy into generating new growth and flowers.

About the Author

Cynthia Domenghini holds a Ph.D. and bachelor's degree in horticulture, as well as a master's degree in teaching. She spent several years researching health outcomes of school gardening and has written numerous youth garden curricula and activity guides. Domenghini also served as an education specialist for the National Gardening Association.